Synthesis and spectroscopic characterization of new mono- and binuclear complexes of some NH(1) thiosemicarbazides

4-Ethylthiosemicarbazide and its NH(1) derivatives have been prepared and confirmed by elemental analysis and ¹H?NMR spectra to produce diverse complexes with Co(II), Ni(II) and Cu(II) ions. The obtained complexes have been investigated based on elemental and thermal analyses, spectral (UV/VIS, ESR, mass) studies and magnetic measurements. The IR data reveal the presence of variable modes of chelation for the investigated ligands. The electronic spectra of the complexes as well as their magnetic moments provide information about geometries. The ESR spectra give evidence for the proposed structure and the bonding for some Cu(II) complexes. Thermal decomposition of some complexes ended with metal or metal oxide as a final product.     

Salisaldehyde-2-aminobenzimidazole schiff base complexes of Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)

New metal complexes of Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with salicylidine-2-aminobenzimidazole (SABI) are synthesized and their physicochemical properties are investigated using elemental and thermal analyses, IR, conductometric, solid reflectance and magnetic susceptibility measurements. The base reacts with these metal ions to give 1:1 (Metal:SABI) complexes; in cases of Fe(III), Co(II), Cu(II), Zn(II) and Cd(II) ions; and 1:2 (Metal:SABI) complexes; in case of Ni(II) ion. The conductance data reveal that Fe(III) complex is 2:1 electrolyte, Co(II) is 1:2 electrolyte, Cu(II), Zn(II) and Cd(II) complexes are 1:1 electrolytes while Ni(II) is non-electrolyte. IR spectra showed that the ligand is coordinated to the metal ions in a terdentate mannar with O, N, N donor sites of the phenloic -OH, azomethine -N and benzimidazole -N3. Magnetic and solid reflectance spectra are used to infer the coordinating capacity of the ligand and the geometrical structure of these complexes. The thermal decomposition of the complexes is studied and indicates that not only the coordinated and/or crystallization water is lost but also that the decomposition of the ligand from the complexes is necessary to interpret the successive mass loss. Different thermodynamic activation parameters are also reported, using Coats-Redfern method. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis, spectral and thermal studies of Co(II), Ni(II) and Cu(II) complexes 1-(4,6-dimethyl-pyrimidin-2-ylazo)-naphthalen-2-ol

The electronic absorption spectra of 1-(4,6-dimethyl-pyrimidin-2-ylazo)-naphthalen-2-ol is studied in organic solvents of different polarity as well as in buffer solutions of varying pH values at different temperatures and different ratios of methanol. The probable structure of the azodye has been assigned on the basis of spectral studies (IR and (1)H NMR). The effect of Co(II), Ni(II) and Cu(II) ions on the emission spectrum of the free azodye is also assigned. The stoichiometry of the metal complexes is determined spectrophotometrically and conductometrically. Novel complexes of Co(II), Ni(II) and Cu(II) with the pyrimidine azodye have been synthesized and characterized on the basis of elemental analyses, molar conductance, magnetic susceptibility measurements, IR, electronic as well as ESR spectral studies The thermal decomposition of the metal complexes is studied by TGA and DTA techniques. The kinetic parameters like activation energy, pre-exponential factor and entropy of activation are estimated.     

Synthesis and characterization of Co(II), Ni(II), Cu(II) and Zn(II) complexes of tridentate Schiff base derived from vanillin and DL-alpha-aminobutyric acid

Co(II), Ni(II), Cu(II) and Zn(II) complexes of the Schiff base derived from vanillin and dl-alpha-aminobutyric acid were synthesized and characterized by elemental analysis, IR, electronic spectra, conductance measurements, magnetic measurements, powder XRD and biological activity. The analytical data show the composition of the metal complex to be [ML(H(2)O)], where L is the Schiff base ligand. The conductance data indicate that all the complexes are non-electrolytes. IR results demonstrate the tridentate binding of the Schiff base ligand involving azomethine nitrogen, phenolic oxygen and carboxylato oxygen atoms. The IR data also indicate the coordination of a water molecule with the metal ion in the complex. The electronic spectral measurements show that Co(II) and Ni(II) complexes have tetrahedral geometry, while Cu(II) complex has square planar geometry. The powder XRD studies indicate that Co(II) and Cu(II) complexes are amorphous, whereas Ni(II) and Zn(II) complexes are crystalline in nature. Magnetic measurements show that Co(II), Ni(II) and Cu(II) complexes have paramagnetic behaviour. Antibacterial results indicated that the metal complexes are more active than the ligand.     

Spectral, magnetic, thermal, antimicrobial, and eukaryotic DNA studies on acetone [N-(3-hydroxy-2-naphthoyl)]hydrazone complexes

Abstract  

Acetone [N-(3-hydroxy-2-naphthoyl)] hydrazone (H₂AHNH) has been prepared and its structure confirmed by elemental analysis and ¹H NMR spectroscopy. It has been used to produce diverse complexes with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and U(VI)O₂ ions. The complexes obtained have been investigated by thermal analysis, spectral studies (¹H NMR, IR, UV–visible, ESR), and magnetic measurements. IR spectra suggest that H₂AHNH acts as a bidentate ligand. The electronic spectra of the complexes and their magnetic moments provide information about geometries. The ESR spectra give evidence for the proposed structure and the bonding for some Cu(II) complexes. Thermal decomposition of the Ni(II) and Cu(II) complexes afforded metal oxides as final products. Kinetic data were obtained for each stage of thermal degradation of some of the complexes using the Coats–Redfern method. The formation of complexes in solution was studied pH-metrically and the order of their stability constants (log K) was found to be U(VI)O₂ > Cu(II) > Zn(II) > Ni(II) > Cd(II) > Co(II). Antimicrobial and eukaryotic DNA studies were carried out.     

Synthesis,characterization and biological studies of some Co(II), Ni(II) and Cu(II) complexes derived from indole-3-carboxaldehyde and glycylglycine as Schiff base ligand

The Schiff base ligand derived from indole-3-carboxaldehyde(indal) and glycylglycine(glygly) were synthesized and characterized by elemental analysis, IR, electronic spectrum, ¹H NMR and mass spectrum. Co(II), Ni(II) and Cu(II)–indal-glygly Schiff base complexes were synthesized and characterized by elemental analysis, molar conductance, IR, electronic spectra, magnetic measurements, ESR, electrochemical studies, TGA, DSC analysis, XRD and SEM. Conductance measurements indicate that the above complexes are 1:1 electrolytes. IR spectral data show that the ligand is tridentate and the binding sites are azomethine nitrogen, peptide nitrogen and carboxylato oxygen atoms. Electronic spectral measurements indicate tetrahedral geometry for Co(II) and Ni(II) complexes and square planar geometry for Cu(II) complex. Magnetic measurements show weak ferromagnetic behaviour for Co(II) and Ni(II) complexes and paramagnetic behaviour for Cu(II) complex. ESR spectral data shows the ionic link between metal and the Schiff base ligand. The metal complexes are found to be stabilized in the unusual oxidation states of the metal ion during electrolysis. Thermal analysis of the complex indicates that the decomposition takes place in three steps. IR and thermal studies indicate that the fourth position would be occupied by a water molecule in complexes. XRD shows that the complexes have the crystallite size of 31, 40 and 67 nm, respectively. The surface morphology of the complexes was studied by SEM. The antimicrobial activity of the ligand and its complexes were screened by Kirby Bayer Disc Diffusion method. DNA cleavage studies were performed for metal–Schiff base complexes in presence of hydrogen peroxide as oxidant.     

Spectral and thermal studies of divalent transition metal with indole-2-carboxylic acid and 4-substituted hydrazinethiocarbamide

Ternary complexes of Co(II), Ni(II) and Cu(II) with indole-2-carboxylic acid (A) and 4-substituted hydrazinethiocarbamide (L) [4-phenylhydrazinethiocarbamide (L(1)), 4-benzylhydrazinethiocarbamide (L(2)) and 4-(2-propenyl)hydrazinethiocarb-amide (L(3)) were prepared. The structure of the complexes was characterized by microchemical analysis, molar conductance, electronic, IR, (1)H-NMR, mass spectra as well as thermogravimetric studies. An octahedral structure is suggested for Co(II), Ni(II) and Cu(II) ternary complexes.     

Synthesis, Thermal, Electrical and Catalytic Studies of Some Transition Metal Polychelates of Bis-bidentate Schiff Base

Polychelates of Mn（Ⅱ）, Fe（Ⅱ）, Co（Ⅱ）, Ni（Ⅱ）, Cu（Ⅱ）, Zn（Ⅱ） and Cd（Ⅱ） with the bis salen-type ligand derived from 4,4＇-bis[（salicylaldehyde-5）azo]biphenyl and 1,4-diaminobutane have been synthesized. All the polychelalls have been characllrized by elemental analysis, magnetic susceptibility measurements, IR, electronic spectra and thennogravirncuic studies. All the complexes isolated in solid stall are dark coloured and insoluble in water and common organic solvents. The ligand behaves as a bis-bidentall molecule coordinating through the phenolic oxygen and azomethine nitrogen atoms. The thermal decomposition of these metal complexes was investigated by thermogravimetric analysis and data have been analyzed for kinetic parameters using Broido equation. The solid-state electrical conductivity of the ligand and its polychelalls in the form of compressed pellet was studied in the temperaturc range from 313 to 413 K All the polychelalls were found to show semiconducting nature. The Mn（Ⅱ）, Fe（Ⅱ）, Co（Ⅱ） and Ni（Ⅱ） polychelalls have been assessed for the catalytic epoxidation of styrene.     

Spectral,magnetic, thermal,antimicrobial, and eukaryotic DNA studies on acetone [<Emphasis Type="Italic">N</Emphasis>-(3-hydroxy-2-naphthoyl)]hydrazone complexes

Abstract  Acetone [N-(3-hydroxy-2-naphthoyl)] hydrazone (H₂AHNH) has been prepared and its structure confirmed by elemental analysis and ¹H NMR spectroscopy. It has been used to produce diverse complexes with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and U(VI)O₂ ions. The complexes obtained have been investigated by thermal analysis, spectral studies (¹H NMR, IR, UV–visible, ESR), and magnetic measurements. IR spectra suggest that H₂AHNH acts as a bidentate ligand. The electronic spectra of the complexes and their magnetic moments provide information about geometries. The ESR spectra give evidence for the proposed structure and the bonding for some Cu(II) complexes. Thermal decomposition of the Ni(II) and Cu(II) complexes afforded metal oxides as final products. Kinetic data were obtained for each stage of thermal degradation of some of the complexes using the Coats–Redfern method. The formation of complexes in solution was studied pH-metrically and the order of their stability constants (log K) was found to be U(VI)O₂ > Cu(II) > Zn(II) > Ni(II) > Cd(II) > Co(II). Antimicrobial and eukaryotic DNA studies were carried out. Graphical abstract        

Synthesis,spectral, thermal and electrochemical characterization of metal(II) complexes with 1-S-methylcarbodithioate-4-substituted thiosemicarbazides

1-S-Methylcarbodithioate-4-substituted thiosemicarbazides (L¹-L³) have been prepared and confirmed by spectral data and elemental analysis. Co(II), Ni(II), Cu(II), Cd(II) and Zn(II) complexes with L¹-L³ have been prepared and characterized by elemental and thermal analyses, molar conductance, magnetic moment, as well as spectral data (IR, ¹H NMR, mass and electronic spectra). The molar conductance data reveal that the chelates are non-electrolytes. The IR and ¹H NMR spectra showed that L¹-L³ are deprotonated in the complexes and act as binegative SNNS donors. The electronic spectra of the complexes as well as their magnetic moments provide information about geometries. Thermogravimetric analysis of some complexes suggests different decomposition steps and ending with metal sulfide as final product. The redox properties of the complexes are explored by cyclic voltammetry.     

Synthesis and characterization of some pyrimidine, purine, amino acid and mixed ligand complexes

Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes of barbital, thiouracil, adenine, amino acids (methionine, lysine and alanine) and some mixed ligands were prepared and characterized by elemental analyses, IR, electronic spectra, magnetic susceptibility and ESR spectra. Coordination of the metallic centre to the oxygen and nitrogen atoms of barbital, thiouracil, amino acids and coordinate to amino group and nitrogen atom of adenine occurred. Electronic spectra and magnetic susceptibility measurements were utilized to infer the structure of the complexes which are octahedral for Mn(II), Fe(III), Co(II), Ni(II) and Cd(II) and tetrahedral for Mn(II), Cu(II), Zn(II) complexes. ESR spectra were observed for copper complexes with a d(x2)-(y2) ground state with small g(||) values indicating strong interaction between the ligands and their metal ions.     

Surface layer-by-layer chemical deposition reaction for thin film formation of nano-sized metal 8-hydroxyquinolate complexes

The feasibility of a novel and simple layer-by-layer chemical deposition method for the preparation of nano-sized metal 8-hydroxyquinolate complexes has been investigated and reported. Uniform nanocrystalline films have been synthesized via dipping a substrate alternately in metal ion solution followed by ligand solution. The stoichiometry of the as-grown anhydrous Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complex crystals were confirmed from the metal analysis and molar stoichiometric ratio of metal ion to 8-hydroxyquinoline. This was characterized as 1:2 for the Co(II), Ni(II), Cu(II) and Zn(II)–quinolate complexes. The Fe(III)–quinolate thin film was found to exhibit a 1:3 ratio. Electron impact-mass spectra (EI-MS) of all the synthesized thin film metal quinolate complexes were recorded and the results refer to the existence of the molecular ion peak at the corresponding m/z values. Confirmation of such stoichiometric 1:2 and 1:3 ratios were also evident from the (EI-MS) study. The deposited thin films were also subjected to analysis by a scanning electron microscope (SEM) and a particle size ?50 nm was detected. FT-IR and UV–Vis spectroscopy were further used to confirm the structure of the metal 8-hydroxyquinolate complexes. Thermal gravimetric analysis (TGA) was also used to follow up the possible thermal decomposition steps and to calculate the thermodynamic parameters of the nano-sized metal complexes.     

Synthesis, spectroscopic and thermal characterization of some transition metal complexes of folic acid

Compounds having general formula: [M(FO)(Cl)(x)(H(2)O)(y)].zH(2)O, where (M=Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II), FO=folate anion, x=2 or 4, y=2 or 4 and z=0, 1, 2, 3, 5 or 15) were prepared. The obtained compounds were characterized by elemental analysis, infrared as well as electronic spectra, thermogravimetric analysis and the conductivity measurements. The results suggested that all folate complexes were formed by 2:1 molar ratio (metal:folic acid) as a bidentate through both of the two carboxylic groups. The molar conductance measurements proved that the folate complexes are electrolytes. The kinetic thermodynamic parameters such as: E*, DeltaH*, DeltaS* and DeltaG* were estimated from the DTG curves. The antibacterial evaluation of the folic acid and their complexes was also done against some Gram positive/negative bacteria as well as fungi.     

Spectral and thermal studies of divalent transition metal complexes with indole-2-carboxylic acid and 4-substituted hydrazinethiocarbamide

Ternary complexes of Co(II), Ni(II) and Cu(II) with indole-2-carboxylic acid (A) and 4-substituted hydrazinethiocarbamide (L) [4-phenylhydrazinethiocarbamide (L1), 4-benzylhydrazinethiocarbamide (L2) and 4-(2-propenyl)hydrazinethiocarbamide (L3)] were prepared. The structures of the complexes were proposed by molar conductance, electronic, IR, 1H NMR, mass spectra as well as thermogravimetric (TG) studies. An octahedral structure is suggested for Co(II), Ni(II) and Cu(II) ternary complexes.     

Synthesis,structural studies and bio-activity of some metal(II) complexes with glyoxal salicylaldehyde acyldihydrazones

Complexes of the type [M(gssdh)]Cl and [M(gspdh)]Cl, where M?=?Co(II), Ni(II), Cu(II), Zn(II) and Cd(II), Hgssdh?=?glyoxal salicylaldehyde succinic acid dihydrazone and Hgspdh?=?glyoxal salicylaldehyde phthalic acid dihydrazone, have been synthesized and characterized by elemental analyses, molar conductance, magnetic moments, electronic, ESR and IR spectra and X-ray powder diffraction studies. The metal complexes are insoluble in common organic solvents and are 1?:?1 electrolytes. The magnetic moment values and electronic spectra indicate a spin–free octahedral geometry for all Co(II), Ni(II) and Cu(II) complexes. ESR spectral parameters of Cu(II) complexes suggest an elongated tetragonally–distorted octahedral stereochemistry around copper. Both ligands are monobasic hexadentate ligands coordinating through three >C=O, two >C=N– and a deprotonated phenolate group to the metal. X-ray powder diffraction parameters for three of the complexes correspond to an orthorhombic crystal lattice. The complexes show appreciable activity against various fungi and bacteria.     

Molecular structure and spectroscopic studies on novel complexes of coumarin-3-carboxylic acid with Ni(II), Co(II), Zn(II) and Mn(II) ions based on density functional theory

Novel Ni(II), Co(II), Zn(II) and Mn(II) complexes of coumarin-3-carboxylic acid (HCCA) were studied at experimental and theoretical levels. The complexes were characterised by elemental analyses, FT-IR, (1)H NMR, (13)C NMR and UV-Vis spectroscopy and by magnetic susceptibility measurements. The binding modes of the ligand and the spin states of the metal complexes were established by means of molecular modelling of the complexes studied and calculation of their IR, NMR and absorption spectra at DFT(TDDFT)/B3LYP level. The experimental and calculated data verified high spin Ni(II), Co(II) and Mn(II) complexes and a bidentate binding through the carboxylic oxygen atoms (CCA2). The model calculations predicted pseudo octahedral trans-[M(CCA2)(2)(H(2)O)(2)] structures for the Zn(II), Ni(II) and Co(II) complexes and a binuclear [Mn(2)(CCA2)(4)(H(2)O)(2)] structure. Experimental and calculated (1)H, (13)C NMR, IR and UV-Vis data were used to distinguish the two possible bidentate binding modes (CCA1 and CCA2) as well as mononuclear and binuclear structures of the metal complexes.     

Copper(II), Nickel(II) and Cobalt(II) Complexes of Dibasic Tridentate Schiff Bases

Complexes of Cu(II), Ni(II) and Co(II) with the Schiff bases derived from o-aminobenzoic acid with salicylaldehyde and its 5-chloro and 5-bromo derivatives have been prepared. The 1:1 (metal-ligand) stoichiometry of these complexes is shown by elemental analysis, gravimetric estimations and conductometric titrations while the structures of the complexes are proved by i.r. spectra and thermogravimetric analysis. The magnetic susceptibility and electronic spectra of Cu(II) complexes indicate the nonplanar binuclear structures while that of Ni(II) and Co(II) show their paramagnetic octahedral geometry. The molar conductance values in nitrobenzene indicate the nonelectrolytic behaviour of the complexes. The results show that the complexes of the type (Cu·L)₂, Ni·L·3H₂O and Co·L·3H₂O are formed having solvent molecule in coordination with the metal ion. The monopyridine and monoammonia adducts of Cu(II) complexes were found to be monomeric.     

Spectral and thermal studies of 4-(1H-pyrazolo (3,4-d) pyrimidin-4-ylazo) benzene-1,3-diol complexes of cobalt(II), nickel(II) and copper(II)

4-(1H-Pyrazolo (3,4-d) pyrimidin-4-ylazo) benzene-1,3-diol was synthesized and characterized by various spectral and analytical techniques. Semiempirical quantum calculations using the AM1 method have been performed in order to evaluate the geometry and electronic structure of the title azodye in the ground state. The complex formation between Co(II), Ni(II) and Cu(II) ions and the title azodye was studied conductometrically and spectrophotometrically. The spectrophotometric determination of the title metal ions and titration using EDTA are reported. Co(II), Ni(II) and Cu(II) complexes of the title azodye have been synthesized and characterized by elemental analysis, conductivity, magnetic susceptibility, IR, UV-Vis and thermal analysis (TGA and DTA).The spectral and magnetic data suggested the octahedral geometry for Co(II) and Ni(II) complexes while Cu(II) complexes have square planar geometry. The thermal studies confirmed the chemical formulations of the title complexes. The thermal degradation takes place in two or three steps depending on the type of the metal and the geometry of the complexes. The kinetics of the decomposition was examined by using Coats-Redfern relation. The activation energies and other activation parameters (DeltaH, DeltaS and DeltaG) were computed and related to the bonding and stereochemistry of the complexes.     

Complexation and Thermal Studies of Uric Acid with Some Divalent and Trivalent Metal Ions of Biological Interest in the Solid State

Nine new [metal uric acid] complexes [M(Ua) n ]°·XH 2 O have been synthesized. These complexes have been characterized by elemental analysis, X-ray diffraction (XRD), magnetic susceptibility ( w eff. ), FTIR spectra, thermal analysis (TG & DTA), and electronic spectra (UV/visible). Uric acid (HUa) coordinates as a bidentate ligand to Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Al(III), Cr(III) and Fe(III) through the protonated N-7 within the imidazole ring and O-6 within the pyrimidine ring. Uric acid forms neutral metal urate complexes with all the above metal ions. The quantitative compositions were determined as [M(Ua) 2 ·(H 2 O) 2 ]°·XH 2 O where M(II)=Mn, Fe, Co, Ni, Cu, Zn and X=2, 4, 2, 4, 2, 2, respectively. The M(II) complexes exhibit an isostructural octahedral coordination with N-7, O-6 of two uric acid ligand molecules, and O of two water molecules. Compositions were also determined as [M(Ua) 3 ]°·YH 2 O where M(III)=Al, Cr, Fe and Y=6, 3, 3 respectively. All the M(III) complexes form an isostructural octahedral coordination with N-7 and O-6 of three uric acid ligand molecules. Iron(III) complexes prepared with N 1 , N 3 and N 9 -methyl uric acid yielded brown complexes with a metal ligand ratio of 1 3, while N 7 -methyl uric acid did not yield a complex due to blockage of N-7 with a methyl group.     

Thermal studies on cobalt(II), nickel(II) and copper(II) ternary complexes of N-(2-acetamido) iminodiacetic acid and imidazoles

The thermal decomposition of Co(II), Ni(II) and Cu(II) complexes has been studied using thermogravimetry (TG) and differential TG (DTG). The complexes have been characterized by IR spectroscopy. The results reveal that the decomposition of these complexes is accompanied by the formation of metal acetate as an intermediate fragments. On the basis of the applicability of a non-isothermal kinetic equations, it was demonstrated that the stability of the complexes follows the order Co(II)>Cu(II)>Ni(II). These stably correspond to the strength of chelation between the metal ions and the primary and secondary ligands. A possible mechanism of the thermal decomposition of the complexes is suggested.